KR101089156B1 - Binder for stack and folding type secondary battery, slurry for electrode, electrode and secondary battery including the binder - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stack and folding type secondary battery binder, an electrode slurry containing the binder, a secondary battery electrode, and a secondary battery, comprising: (a) (meth) acrylic acid ester as a binder for electrode mixture of a stack and folding type secondary battery; It includes polymer particles polymerized into a single phase by using a monomer containing at least one monomer selected from the group monomer, (b) acrylate monomer and vinyl monomer group, and (c) a nitrile group represented by the formula (1) It relates to a secondary battery binder.

[Formula 1]

(Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is a C1 to C18 hydrocarbon group.)

According to the binder of the present invention, the adhesion between the active material and the active material, between the active material and the current collector, as well as the active material and the polymer separator is excellent, and the lamination characteristics of the separator are good, thereby improving the performance of the stack-and-fold battery.

Secondary Battery, Binder, Stack and Folding, Adhesiveness, Separator

Description

Stackable and folding type secondary battery binder, slurry for electrode including the binder, secondary battery electrode and secondary battery TECHNICAL FIELD

The present invention relates to a stack-and-fold type secondary battery binder, an electrode slurry including the binder, a secondary battery electrode, and a secondary battery, and more particularly, between an active material, an active material and a current collector, which are characteristics of existing binders, as well as electrodes. And an aqueous binder having lamination properties through adhesion to a separator.

Recently, as technology development and demand for portable devices such as portable computers, portable telephones, and cameras increase, the demand for secondary batteries used as energy sources of these electronic devices is rapidly increasing. Among them, lithium ion secondary batteries have been researched and widely commercialized due to the advantages of high energy density, high voltage, and long life.

Conventionally, a typical lithium secondary battery uses graphite as a negative electrode active material, and charging and discharging are performed while repeating a process of intercalating and deintercalating lithium ions of a positive electrode. The theoretical capacity of the battery is different depending on the type of electrode active material, but as the cycle progresses, the charge and discharge capacity is generally lowered. This phenomenon is most likely due to the separation of the electrode active material or between the electrode active material and the current collector due to the volume change of the electrode generated as the charge and discharge of the battery proceeds, so that the active material does not perform its function. In addition, during the insertion and desorption process, lithium ions inserted into the negative electrode do not escape properly, thereby reducing the active point of the negative electrode. As a result, the charge and discharge capacity and life characteristics of the battery may decrease as the cycle progresses. In particular, in order to increase the discharge capacity, when a combination of materials such as silicon, tin, and silicon-tin alloy with high discharge capacity is mixed with natural graphite having a theoretical discharge capacity of 372 mAh / g, charge and discharge may be As it progresses, the volume expansion of the material is significantly increased, which causes the separation of the negative electrode material from the electrode material and eventually causes a problem that the capacity of the battery is sharply reduced when several cycles are performed.

Therefore, the strong adhesion to prevent desorption between the electrode active material or between the electrode active material and the current collector and to control the volume expansion of the electrode active material generated during repeated charging and discharging to improve the structural stability of the electrode and thereby improve the performance of the battery. There is an urgent need in the art for research on possible binder and electrode materials.

Since polyvinylidene fluoride (PVdF), which is a conventional solvent-based binder, does not meet the above requirements, emulsion particles are prepared by polymerizing styrene-butadiene rubber (SBR) in an aqueous phase from recent years. A method of mixing with a thickener and the like has been proposed and is currently used commercially. In the case of such a binder, there is an advantage that the battery capacity can be increased by reducing the amount of binder used and environmentally friendly. However, even in this case, although the adhesion sustaining force is improved by the elasticity of the rubber, the adhesive force itself does not show a great effect, and the improvement of battery characteristics is also required.

On the other hand, the secondary battery is based on a unit cell composed of a positive electrode, a negative electrode and a separator interposed between the positive electrode and the negative electrode, and is largely divided into a jelly roll type (winding type) and a stack type (lamination type) according to the cell structure. The jelly roll type is prepared by coating the positive and negative electrodes on a metal foil and pressing them, cutting them into bands of a desired width and length, and winding the spirals after separating the negative electrode and the positive electrode using a separator film. Such jelly roll structures are widely used in the manufacture of cylindrical batteries, but due to the small radius of rotation of the central portion of the spiral, excessive stresses are formed at the curved surfaces of the electrodes, which often causes peeling problems of the electrodes. On the other hand, the stack type is a structure in which a plurality of anode and cathode unit cells are sequentially stacked, and the shape of the rectangle is easy to obtain, but when the manufacturing process is complicated and an impact is applied, the electrode is pushed to cause a short circuit. There are disadvantages.

In order to solve this problem, the electrode assembly of the jelly roll-type and stack-type structure, a full cell or anode (cathode) / separator / cathode (anode) / separator / anode of a certain unit size of anode / separator / cathode structure A stack-and-fold type electrode assembly has been developed in which a bi-cell having a (cathode) structure is folded using a long continuous film. This is disclosed in Korean Patent Application Laid-Open Nos. 2001-82058, 2001-82059, 2001-82060, and the like.

In the stack-and-fold type electrode assembly, the positive electrode and the negative electrode are bonded by thermal fusion of the separator, but the adhesion between the active material and the separator becomes an important factor. Currently commercially available SBR binders do not adhere when the polymer separator and the electrode plate are thermally fused, thus causing problems that are not suitable for use in a stack-and-fold type electrode assembly. Conventional binders have been studied in order to increase the adhesion between the active material and the active material, the adhesion between the active material and the current collector, but the research related to the adhesion between the active material and the polymer separator has not been reported yet.

The present invention is to solve the above problems, to provide a binder for a stack and folding type secondary battery excellent in adhesion between the active material, the active material and the current collector, as well as the electrode and the separator, which is a characteristic of the existing binder. There is a purpose.

Another object of the present invention is to prepare a single-phase polymer having the same composition through emulsion polymerization, unlike an SBR binder in which two or more polymers have different chemical structures in the form of two or more composite polymers.

It is still another object of the present invention to provide a slurry for an electrode containing the binder, an electrode manufactured from the slurry, and a secondary battery including the electrode, which improve performance of a stack-and-fold type secondary battery through excellent lamination characteristics with a polymer separator. To provide.

The present invention is to achieve the above object, it is selected from the group of (a) (meth) acrylic acid ester monomers, (b) acrylate monomers and vinyl monomers as a binder for electrode mixture of a stack and folding secondary battery Provided is a secondary battery binder comprising at least one monomer and (c) polymer particles polymerized into a single phase using a monomer containing a nitrile group represented by the following formula (1).

[Formula 1]

(Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is a C1 to C18 hydrocarbon group.)

In addition, the (meth) acrylic acid ester monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n-ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate propyl methacrylate isopropyl methacrylate, n-butyl methacrylate, isobutyl Methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl It is characterized by at least one member selected from the group consisting of methacrylate.

In addition, the acrylate monomers are methacryloxyethyl ethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene diacrylate, ditrimethylpropane tetraacrylate, hydroxy ethyl acrylate, dipenta Erythriol hexaacrylate, pentaerythriol triacrylate, pentaerythriol tetraacrylate, lauryl acrylate, seryl acrylate, stearyl acrylate, lauryl methacrylate, cetyl methacrylate and stearyl It is characterized in that at least one member selected from the group consisting of methacrylate.

In addition, the vinyl monomer is characterized in that at least one member selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t- butyl styrene and divinylbenzene.

The (meth) acrylic acid ester monomer may be included in an amount of 5 to 95 parts by weight based on 100 parts by weight of the binder polymer.

The copolymer may include one or more monomers selected from the group consisting of (meth) acrylamide monomers or oligomers thereof and unsaturated monocarboxylic acid monomers.

In addition, the (meth) acrylamide monomer or oligomer thereof is one or more selected from the group consisting of acrylamide, n-methylolacrylamide, n-butoxymethylacrylamide and methacrylamide, and the unsaturated mono The carboxylic acid monomer is at least one member selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, metaconic acid, glutamic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid. It is characterized by.

In addition, the present invention is (a) the binder of any one of claims 1 to 7; And (b) an electrode slurry including an electrode active material capable of occluding and releasing lithium.

In addition, the present invention provides an electrode for secondary batteries, wherein the slurry is applied to the current collector.

In addition, the present invention is the positive electrode and the negative electrode of the above electrode; A separator interposed between the anode and the cathode; And it provides a secondary battery comprising an electrolyte.

In addition, the secondary battery is characterized in that it comprises a lamination process that requires adhesion to the polymer film during the cell assembly process.

In addition, the secondary battery is heat-sealed the electrode plate and the polymer separator at a temperature between 10 ~ 200 ℃ the bicell of the anode / separator / cathode or anode (cathode) / separator / cathode (anode) / separator / anode (cathode) It is characterized by folding using a long separation film of a long length.

According to the binder of the present invention, the adhesion between the active material and the active material, between the active material and the current collector, as well as the active material and the polymer separator is excellent, and the lamination characteristics of the separator are good, thereby improving the performance of the stack-and-fold battery.

The present invention provides a binder for electrode mixture of a stack and folding secondary battery, (a) (meth) acrylic acid ester monomer, (b) at least one monomer selected from acrylate monomer and vinyl monomer group, and (c) The present invention relates to a secondary battery binder including polymer particles polymerized into a single phase by using a monomer including a nitrile group represented by the following formula (1).

[Formula 1]

(Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is a C1 to C18 hydrocarbon group.)

Hereinafter, the present invention will be described in detail.

The acrylic ester monomer is preferably methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n- One or more selected from the group consisting of ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate mixture, but is not limited to these.

The methacrylic acid ester monomer is preferably methyl methacrylate, ethyl methacrylate propyl methacrylate isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, Group consisting of isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate or mixtures thereof One or more selected from, but is not limited to these.

The (meth) acrylic acid ester monomer may be included in an amount of 5 to 95 parts by weight based on 100 parts by weight of the binder polymer, and may be used by appropriately changing the type and content of the monomer according to the properties and physical properties of each monomer. When less than 5 parts by weight or more than 95 parts by weight, the adhesive strength of the binder is significantly lowered, which is not preferable.

The acrylate-based monomers are methacryloxyethyl ethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene diacrylate, ditrimethyllopropane tetraacrylate, hydroxyethyl acrylate, dipentaerythrone All hexaacrylates, pentaerythriol triacrylate, pentaerythriol tetraacrylate, lauryl acrylate, seryl acrylate, stearyl acrylate, lauryl methacrylate, cetyl methacrylate and stearyl meta acrylate It may be one or more selected from the group consisting of the rate.

The vinyl monomer may preferably be at least one selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, divinylbenzene, and mixtures thereof.

The content of at least one monomer selected from the group of acrylate monomers and vinyl monomers may be included in an amount of 1 to 70 parts by weight based on 100 parts by weight of the binder polymer, and when included in an amount of less than 1 part by weight, adhesion and coating properties are remarkably increased. It is not preferable because it may be lowered, and if it exceeds 70 parts by weight, the stability is lowered during the manufacturing process, making the manufacturing difficult, which is not preferable.

As the nitrile group-containing compound, a compound represented by the following general formula (1) is used.

[Formula 1]

(Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is a C1 to C18 hydrocarbon group.)

Examples of the nitrile group-containing compound represented by Formula 1 may include 3-vinyloxypropanenitrile, 4-vinyloxybutanenitrile, and the like, and may be one or more selected from the group consisting of these compounds alone or mixtures thereof.

The content of the nitrile group-containing compound represented by Chemical Formula 1 may be included in an amount of 1 to 80 parts by weight based on 100 parts by weight of the binder polymer. If it exceeds, since polymerization stability falls, it is unpreferable.

The binder of the present invention may further include monomers commonly used in the art, in particular one or more monomers selected from the group consisting of (meth) acrylamide monomers and unsaturated monocarboxylic acid monomers. Can be added.

The (meth) acrylamide monomer may preferably be acrylamide, n-methylol acrylamide, n-butoxymethylacrylamide, methacrylamide, or a mixture thereof, and the unsaturated monocarboxylic acid monomer may be Preferably maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutamic acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, nadic acid, or mixtures thereof, but are not limited thereto.

The monomers may improve adhesion between the current collector and the electrode active material, and between the electrode active material and the electrode active material. However, since the polymerization of the binder may be difficult when the added monomer is contained in an excessive amount, it may be preferably added in an amount of 1 to 20 parts by weight based on 100 parts by weight of the binder polymer.

The method of polymerizing the monomers according to the present invention is not particularly limited, and may be, for example, by bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, and the like. The polymerization temperature and polymerization time may be determined by the polymerization method or the polymerization initiator used. It may be appropriately selected depending on the type, the polymerization temperature may be about 50 to 200 ℃, the polymerization time may be 1 to 20 hours.

The polymerization initiator may be used an inorganic or organic peroxide, for example, a water-soluble initiator including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, and an oil-soluble initiator including cumene hydroperoxide, benzoyl peroxide, and the like. Can be used. In addition, the polymerization initiator may further include an activator to promote the initiation reaction of the peroxide, wherein the activator is sodium formaldehyde sulfoxylate, sodium ethylenediamine tetraacetate, ferrous sulfate and dextrose It may be one or more selected from the group consisting of.

The binder of the present invention may use a molecular weight regulator, a crosslinking agent and a grafting agent as a polymerization additive in addition to the monomer.

The crosslinking agent is, for example, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate Neopentyl glycol dimethacrylate, trimethylol propane trimethacrylate, trimethylol methane triacrylate, and the like. As the grafting agent, aryl methacrylate (AMA), triaryl isocyanurate (TAIC), triaryl amine (TAA), diaryl amine (DAA) and the like are used.

In the present invention, an emulsifier may be used during emulsion polymerization or suspension polymerization. The emulsifier may be, for example, a fatty acid salt system represented by oleic acid, stearic acid, lauric acid, sodium or potassium salt of mixed fatty acids, rosin acid, or the like. General anionic emulsifiers and the like can be used, preferably a reactive emulsifier to improve the stability of the latex may be added. The said emulsifier can be used individually or in mixture of 2 or more types.

The present invention also provides a slurry for electrodes comprising the binder composition and an electrode active material capable of occluding and releasing lithium. At this time, the slurry is used as a mixture of conventional additives known in the art as needed.

The electrode active material is an important substance for determining the capacity of the battery, and is not particularly limited as long as it can occlude and release lithium. Non-limiting examples of the positive electrode active material of the electrode active material is a layered compound such as oxide, lithium cobalt, nickel oxide, compound substituted with one or more transition metals, lithium manganese oxide, lithium copper oxide, vanadium oxide, lithium manganese composite oxide, Disulfide compounds and the like. Non-limiting examples of the negative electrode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon; Conductive polymers such as polyacene; Metals such as Al, Si, Sn, Ag, Bi, Ma, Zn, In, Ge, Pb, Pd, Pt, Ti which can be alloyed with lithium, and compounds containing these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitrides, and the like. Among them, carbon-based active materials, silicon-based active materials, tin-based active materials, and silicon-carbon-based active materials are more preferable, and these may be used alone or in combination of two or more.

In addition to the electrode active material and the binder, the electrode slurry according to the present invention may further include other components, such as a dispersion medium, a conductive material, a viscosity regulator, a filler, a coupling agent, an adhesion promoter, or a combination of two or more thereof.

The present invention also provides an electrode for secondary batteries in which the electrode mixture is coated on a current collector.

In the electrode, the current collector is a portion where electrons move in the electrochemical reaction of the active material, and a negative electrode current collector and a positive electrode current collector exist according to the type of electrode.

The electrode is manufactured according to a conventional method known in the art, for example, a slurry for battery electrodes, which is a mixture of an active material mixed with the binder composition, is applied to a current collector, and the dispersion medium is dried, for example. By removing the binder to bind the active material to the current collector, the active material is bound together to prepare an electrode.

The current collector is not particularly limited as long as it is usually made of a conductive material, but usually a metal made of iron, copper, aluminum, nickel or the like is used.

The present invention also provides a lithium secondary battery comprising the electrode. The lithium secondary battery has a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated into an electrode assembly having a separator interposed between a positive electrode and a negative electrode.

The lithium secondary battery of the present invention is not particularly limited in appearance and includes a manufacturing process that requires adhesion with a polymer film, and preferably provides a lithium secondary battery having a stack-and-fold structure.

The stack-and-folding structure may include an anode; a separator; an anode; a separator; a bicell in which the anode is positioned, or a cathode in a sequential order; a separator; an anode; a separator; Each of the overlapping portions of the cell is sandwiched by a separator film and pressed at the appropriate temperature by roll lamination to bond the separator film to the cell.

The separator is preferably a porous separator, and non-limiting examples thereof include a polypropylene-based, polyethylene-based or polyolefin-based porous separator.

In the following Examples, Comparative Examples and Experimental Examples will be described in more detail, but the present invention is not limited thereto.

Example 1

1-1 Preparation of Binder Composition

225 g of ion-exchanged water was introduced into the reactor and the temperature was raised to 75 ° C. When the temperature of the ion-exchanged water reaches 75 ° C., 60 g of butyl acrylate, 30 g of styrene, 5 g of 3-vinyloxypropanenitrile, 3 g of acrylic acid, and 0.5 g of aryl methacrylate are added to the reaction mixture in 4 hours. 1 g of potassium persulfate was dissolved in 30 g of ion-exchanged water, and then divided into 4 hours for the reaction to proceed.

1-2 Preparation of the electrode

95 parts by weight of natural graphite using water as a dispersion medium, 2.5 parts by weight of carboxymethyl cellulose, which is a water-soluble polymer, was mixed with 2.5 parts by weight of the binder composition prepared in Example 1-1 to prepare a negative electrode active material slurry, and coated on copper foil. After drying, it was compressed to prepare a negative electrode.

NMP (N-methyl-2-pyrrolidone) is used as a dispersion medium, 94 parts by weight of LiCoO2 as an active material, 1 part by weight of a conductive polymer, and 5 parts by weight of PVDF binder are mixed to prepare a slurry, coated on aluminum foil, dried, and then compressed. A positive electrode was prepared.

1-3 Fabrication of Lithium Secondary Battery

The double-coated anode prepared in Example 1-2 was cut except for a tab to make a rectangle of 2.9 cm x 4.3 cm, and the double-coated cathode was tabbed into a rectangle of 3.0 cm x 4.4 cm. The cell was cut except for the seat, and the polymer film was cut and placed between the anode and the cathode to a size of 3.1 cm x 4.5 cm, and then passed through a roll laminator at 100 ° C. to bond each electrode and the separator by heat fusion to prepare a full cell. .

The full cells prepared above were cut into polymer parts having a size of 3.1 cm x 4.5 cm and placed in the overlapped parts, and then passed through a roll laminator at 100 ° C., thereby bonding each full cell and the polymer film by heat fusion.

The prepared full-cell battery was placed in an aluminum laminate packaging material, and a liquid electrolyte having a weight composition of 1 M LiPF6 concentration of EC (Ethyl Carbonate): PC (Propylene Carbonate): DEC (Diethyl Carbonate) = 3: 2: 5 was injected and packaged. .

[Example 2]

Except for using 4-vinyloxybutanenitrile instead of 3-vinyloxypropanenitrile, the same method as in Examples 1-1 to 1-3, and the binder composition, the electrode prepared using the binder composition and the A lithium secondary battery having an electrode was manufactured.

Example 3

Except that the amount of 3-vinyloxypropanenitrile was increased to 10g by the same method as in Examples 1-1 to 1-3 to provide a binder composition, an electrode prepared using the binder composition and the electrode A lithium secondary battery was prepared.

Comparative Example 1

Except that the negative electrode was prepared by using a negative electrode slurry prepared by dispersing NMP as a dispersion medium, 95 parts by weight of natural graphite, 1 part by weight of Super-P (conductive agent), 4 parts by weight of PVDF binder and dispersed therein. A lithium secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 2

A negative electrode was manufactured in the same manner as in Example 1, except that Styrene-Butadiene Rubber latex binder was used instead of the prepared binder of Example 1-1.

Comparative Example 3

A lithium secondary battery having a binder composition, an electrode manufactured using the binder composition, and a lithium secondary battery provided with the electrode by performing the same method as Examples 1-1 to 1-3 except that 5 g of 3-vinyloxypropanenitrile was not added thereto. Manufactured

The adhesion of the Examples and Comparative Examples prepared by each method was measured, and the life characteristics were measured while charging and discharging in the voltage range of 3V to 4.2V for each of the five batteries manufactured. In order to measure the adhesive force between the electrode active material and the separator film, the prepared electrode and the separator film were heat-sealed with a roll laminator at 100 ° C., and then peeled off to confirm the ratio of the electrode active material remaining in the separator film. Figures 1 to 3 (Example 1, Comparative Example 1 and Comparative Example 2) are shown in the separator plate and the electrode plate and the separator after lamination.

200 cycle efficiency (%) Electrode Adhesion (g) Remaining Electrode Active Material Amount (%) Example 1 86 36 28 Example 2 85 34 23 Example 3 89 38 26 Comparative Example 1 78 17 0 Comparative Example 2 83 28 0 Comparative Example 3 82 21 23

As shown in Table 1, the binders of Examples 1 to 3 prepared by using the monomer represented by Chemical Formula 1 were prepared by dissolving PVDF in a solvent (Comparative Example 1) and Styrene-Butadiene Rubber, which are used in the past. Compared to the water-based binder (Comparative Example 2) of the type showed a significantly improved adhesion. Also, except for the 3-vinyloxypropanenitrile monomer, Example 1 showed excellent adhesive properties compared to the binder of Comparative Example 3 having the same composition as in Example 1.

This can be seen that the monomer of the general formula (1) has a great effect on improving the adhesion, the adhesion varies depending on the monomer type, but greatly improves the overall adhesion.

As shown in Table 1, when measuring the adhesion with the separator film, PVdF (Comparative Example 1) and Styrene-Butadiene Rubber type of water-based binder (Comparative Example 2) that is used in the past has a surface adhesive force with the separator film In contrast, when there is no active material adhered to the separator film when it is removed after roll lamination, the polymer (Example 3) according to the present invention has a surface adhesive force with the separator film, so that the negative electrode active material remains on the separated separator film. It can be seen that. This is considered to be because the acrylic ester monomer of the binder of the present invention has a lot of distribution on the surface of the electrode plate, which is superior to other binders (Comparative Examples 1 and 2).

This can be confirmed even by comparing the picture taken out of the separator and the separator after separation and lamination in Example 1 and Comparative Examples 1 and 2 of the present invention.

In addition, in the case of using the binder according to the present invention (Examples 1, 2 and 3), the battery characteristics are improved compared to the conventional Styrene-Butadiene Rubber type binders (Comparative Example 2) and solvent-based binders (Comparative Example 1). This may be explained for the following reasons. The volume expansion that occurs during charging and discharging of the battery generates stress, which causes cracks in the electrode and degrades the cycle performance of the battery due to irreversible occurrence at the crack surface. In addition, it is impossible to prevent the electrode from being detached from the current collector during charge and discharge of the battery due to the weakening of the adhesive force of the electrode. Therefore, the binder of the present invention is strong enough to prevent desorption of the electrode, and the cycle efficiency of the battery is considered to be increased compared to other binders due to the excellent lamination property with the separator as well as the adhesion between the active materials.

Therefore, the secondary battery including the binder according to the present invention has overall excellent battery characteristics with improved high capacity and cycle characteristics.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the secondary battery including the binder according to the present invention has overall excellent battery characteristics with improved high capacity and cycle characteristics.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

1 is a picture taken out of the separator and the separator after the separation membrane and Example 1 of the present invention.

Figure 2 is a picture of the separator and the separator after lamination of the separator of Comparative Example 1 of the present invention.

Figure 3 is a picture of the separation plate and the separator after the separation membrane and the lamination of Comparative Example 2 of the present invention.

Claims (12)

(B) at least one monomer selected from the group consisting of (a) (meth) acrylic acid ester monomers, (b) acrylate monomers and vinyl monomers as a binder for electrode mixture of a stack and folding type secondary battery, and (c) A secondary battery binder comprising polymer particles polymerized into a single phase using a monomer containing a nitrile group represented by. [Formula 1]

(Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is a C1 to C18 hydrocarbon group.) The method of claim 1, The (meth) acrylic acid ester monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n- Ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate propyl methacrylate isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate Latex, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate A secondary battery binder, characterized in that at least one member selected from the group consisting of a rate. The method of claim 1, wherein the acrylate monomer is methacryloxyethyl ethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene diacrylate, ditrimethyllopropane tetraacrylate, hydroxy ethylacryl Latex, dipentaerythrol hexaacrylate, pentaerythroli triacrylate, pentaerythroli tetraacrylate, lauryl acrylate, seryl acrylate, stearyl acrylate, lauryl methacrylate, cetyl methacrylate At least one member selected from the group consisting of latex and stearyl methacrylate. The binder for secondary batteries according to claim 1, wherein the vinyl monomer is at least one selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, and divinylbenzene. The binder for secondary batteries according to claim 1, wherein the (meth) acrylic acid ester monomer is included in an amount of 5 to 95 parts by weight based on 100 parts by weight of the binder polymer. The secondary battery binder according to claim 1, wherein the copolymer comprises one or more monomers selected from the group consisting of (meth) acrylamide monomers or oligomers thereof and unsaturated monocarboxylic acid monomers. The method according to claim 6, wherein the (meth) acrylamide monomer or oligomer thereof is one or more selected from the group consisting of acrylamide, n-methylolacrylamide, n-butoxymethylacrylamide and methacrylamide. , The unsaturated monocarboxylic acid-based monomer is from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, metaconic acid, glutamic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid A secondary battery binder, characterized in that at least one selected. (a) the binder of any one of claims 1-7; And (b) an electrode active material capable of occluding and releasing lithium Slurry for electrodes comprising a. The electrode for secondary batteries in which the slurry of Claim 8 is apply | coated to the electrical power collector. An anode and a cathode of the electrode of claim 9; A separator interposed between the anode and the cathode; And Secondary battery comprising an electrolyte. The secondary battery of claim 10, wherein the secondary battery comprises a lamination process requiring adhesion to a polymer film during cell assembly. The method of claim 10, The secondary battery heat-bonds the electrode plate and the polymer separator at a temperature between 10 ° C. and 200 ° C. in a bicell of a cathode / separator / cathode or a cathode (cathode) / separator / cathode (anode) / separator / anode (cathode). A secondary battery characterized in that it is folded using a continuous separation film of a long length.

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